Carbonization method and graphitization method of carbon fiber

Abstract

The invention discloses a carbon fiber carbonization method and graphitization method, and the carbonization method comprises the following steps: adopting microwave plasma torch equipment as carbonization equipment, adopting inert gas as plasma gas, enabling a pre-oxidized fiber to pass through a plasma torch of a microwave plasma torch, and carrying out carbonization reaction on the pre-oxidized fiber; the number of the microwave plasma torches is at least two, each microwave plasma torch corresponds to a carbonization reaction temperature zone, and the at least two microwave plasma torches sequentially form a low-temperature carbonization zone and a high-temperature carbonization zone with the temperature gradually increased in the moving direction of the pre-oxidized fiber; according to the method, the microwave plasma torches are adopted as carbonization equipment and graphitization equipment, carbonization and graphitization areas can be flexibly increased and decreased, the performance of the carbon fibers is improved, meanwhile, the equipment cost and the operation cost are greatly reduced, and the energy utilization rate is increased.

Description

Technical Field

[0001] The invention relates to a carbonization method and a graphitization method of carbon fiber. Background Art

[0002] Carbon fiber (CF) has high specific modulus and high specific strength, electrical conductivity, corrosion resistance and other excellent physical properties, which makes CF have broad application prospects in the fields of national defense, aerospace and high-end civilian products. For polyacrylonitrile-based carbon fiber, each link in a series of process flows such as polymerization of acrylonitrile, preparation of precursor, pre-oxidation carbonization, etc. will affect the final performance of the carbon fiber material. Invention patent CN202110817829.0 points out that increasing the carbonization temperature zone can significantly improve fiber performance and reduce carbonization time. However, traditional carbonization furnaces and graphitization furnaces are large in structure and expensive, and it is very difficult to increase the carbonization temperature zone. The inert gas microwave plasma equipment used in the present invention has a compact structure, is easy to install, and has low operating costs. It provides a practical solution for increasing the carbonization temperature zone and optimizing the carbonization process.

[0003] Due to the constraints of foreign technology blockade and high production costs, domestic carbon fiber companies have difficulty in making profits in recent years, and their performance is different from that of products of companies such as Toray. The application and promotion of carbon fiber is also limited by high costs. Therefore, how to reduce costs and increase efficiency and improve product performance has become a difficult problem for major carbon fiber companies. The high-temperature carbonization furnace and graphitization furnace of carbon fiber of existing carbon fiber production enterprises are graphite furnaces, which are generally more than 5 meters in length, with a power of more than 100kw, and a price of millions or even tens of millions. The operation and maintenance costs are expensive, and the heating and cooling processes are slow. Due to the structure of the sintering furnace, a large amount of energy is wasted on heating the furnace and cooling water, the energy utilization rate is very low, and a large amount of inert gas is also required. The expensive price and operating cost also limit the number of carbonization and graphitization temperature zones. At present, the carbonization and graphitization processes of traditional carbon fiber production lines are generally completed using low-temperature carbonization furnaces, high-temperature carbonization furnaces and graphitization furnaces. Due to the size and power of the furnace body, the number of temperature zones in the furnace is small and fixed, and it is difficult to optimize the carbonization and graphitization processes by increasing the number of temperature zones. Therefore, reducing the cost and power of carbonization equipment, reducing energy consumption, and reducing gas consumption are the best ways to reduce costs and increase efficiency. Improving carbon fiber production equipment to flexibly control the number of carbonization and graphitization temperature zones and temperature gradient distribution is also an effective way to improve carbon fiber performance. Summary of the invention

[0004] The present invention aims to overcome the problems of expensive carbon fiber carbonization and graphitization equipment, high carbonization energy consumption, serious energy waste, low production efficiency and high production cost, and further provide a carbon fiber carbonization method and graphitization method. The present invention uses inert gas microwave plasma as a heating method to carbonize pre-oxidized filaments in a plasma flame, opening up a new carbon fiber preparation route, reducing energy consumption and cost in carbon fiber preparation, and improving production efficiency.

[0005] The present invention solves the above technical problems through the following technical solutions:

[0006] The present invention provides a carbonization method of carbon fiber, which comprises the following steps:

[0007] A microwave plasma torch device is used as a carbonization device and an inert gas is used as a plasma gas, and a pre-oxidized wire is passed through a plasma torch of the microwave plasma torch to perform a carbonization reaction on the pre-oxidized wire;

[0008] The number of the microwave plasma torches is at least 2, each of the microwave plasma torches corresponds to a temperature zone for carbonization reaction, and at least 2 of the microwave plasma torches sequentially form a low-temperature carbonization zone and a high-temperature carbonization zone with gradually increasing temperature along the moving direction of the pre-oxidized wire;

[0009] The low temperature carbonization zone includes at least one temperature zone, and the temperature of the low temperature carbonization zone is 350-800°C;

[0010] The high temperature carbonization zone includes at least one temperature zone, and the temperature of the high temperature carbonization zone is 800-1600°C.

[0011] In the present invention, the temperature difference between adjacent temperature zones is preferably 50-500°C, more preferably 50-250°C.

[0012] In the present invention, the number of the microwave plasma torches is preferably 6 to 10, more preferably 8.

[0013] The low-temperature carbonization zone preferably includes three temperature zones with gradually increasing temperature along the moving direction of the preoxidized wire, and the temperatures of the three temperature zones are preferably 350-400°C, 550-650°C and 700-800°C, for example, 350°C, 600°C and 800°C.

[0014] Wherein, the high-temperature carbonization zone preferably includes 5 to 7 temperature zones with gradually increasing temperatures along the moving direction of the pre-oxidized wire.

[0015] When there are five temperature zones, the temperatures of the five temperature zones are preferably 850-950°C, 1000-1100°C, 1150-1250°C, 1300-1400°C and 1450-1550°C, for example, 920°C, 1030°C, 1160°C, 1350°C and 1500°C;

[0016] When there are 7 temperature zones, the temperatures of the 7 temperature zones are preferably 850-950°C, 1000-1100°C, 1150-1200°C, 1230-1300°C, 1320-1400°C, 1420-1500°C and 1550-1650°C, for example 920°C, 1030°C, 1160°C, 1280°C, 1350°C, 1460°C and 1600°C.

[0017] In the present invention, the reaction time in each temperature zone is preferably 3 to 20 seconds, such as 4 seconds, 5 seconds, 7 seconds, 10 seconds or 20 seconds.

[0018] In the present invention, the running speed of the pre-oxidized wire in the microwave plasma torch is preferably 3 to 20 m / min, such as 5 m / min, 10 m / min or 20 m / min.

[0019] In the present invention, the number of the microwave plasma torches may be 4, and the temperatures of the four temperature zones are preferably 350-400° C., 550-650° C., 1100-1200° C. and 1450-1550° C., for example, 350° C., 600° C., 1150° C. and 1500° C. The reaction time of the four temperature zones is preferably 15-25 seconds, for example, 20 seconds.

[0020] In the present invention, the number of the microwave plasma torches may be 6, and the temperatures of the 6 temperature zones are preferably 350-400° C., 550-650° C., 700-800° C., 1000-1100° C., 1200-1350° C. and 1400-1500° C., for example, 350° C., 600° C., 800° C., 1050° C., 1300° C. and 1450° C. The reaction time of the 6 temperature zones is preferably 8-12 seconds, for example, 10 seconds.

[0021] In the present invention, the number of the microwave plasma torches may be 8, and the temperatures of the 8 temperature zones are preferably 350-400° C., 550-650° C., 700-800° C., 850-950° C., 1000-1100° C., 1150-1250° C., 1300-1400° C. and 1450-1550° C., for example, 350° C., 600° C., 800° C., 920° C., 1030° C., 1160° C., 1350° C., 1500° C. The reaction time of the 8 temperature zones is preferably 3-8 seconds, for example, 5 seconds.

[0022] In the present invention, the number of the microwave plasma torches is 10, and the temperatures of the 10 temperature zones are preferably 350-400° C., 550-650° C., 700-800° C., 850-950° C., 1000-1100° C., 1150-1200° C., 1230-1300° C., 1320-1400° C., 1420-1500° C. and 1550-1650° C., for example, 350° C., 600° C., 800° C., 920° C., 1030° C., 1160° C., 1280° C., 1350° C., 1460° C. and 1600° C. The reaction time of the 8 temperature zones is preferably 3-6 seconds, for example, 4 seconds.

[0023] In the present invention, the inert gas is preferably one or more of argon, nitrogen, helium and neon, more preferably argon.

[0024] In the present invention, the flow rate of the inert gas is determined according to the actual number of carbonized fiber bundles and the required flame height. For example, when the number of carbonized fiber bundles is 1 to 5 and each bundle contains 3,000 fibers, the flow rate of the inert gas is preferably 0.5 to 300 L / min, more preferably 5 to 30 L / min, and further preferably 10 to 20 L / min.

[0025] In the present invention, the power of the microwave plasma torch is determined according to the actual number of carbonized fiber bundles. For example, when the number of carbonized fiber bundles is 1 to 5 and each bundle contains 3,000 fibers, the power of each microwave plasma torch is preferably 0.5 to 5 kW, more preferably 1.5 to 3 kW.

[0026] In the present invention, the carbon fiber carbonization method preferably further comprises drafting and conveying the carbon fiber.

[0027] The equipment used for the stretching transmission is conventional in the art, such as a stretching roller.

[0028] The draft ratio of the low temperature carbonization zone is preferably -8% to 8%, more preferably -1.0% to 4.0%. The draft ratio of the high temperature carbonization zone is preferably -6% to 3%, more preferably -4.0% to 0.5%.

[0029] In the present invention, the pre-oxidized yarn refers to the basic material for producing carbon fiber conventionally used in the art.

[0030] In the present invention, the method for preparing the pre-oxidized yarn preferably comprises: subjecting the raw yarn to oxidation treatment in an oxidation furnace to obtain the pre-oxidized yarn.

[0031] Wherein, the temperature of the oxidation treatment is preferably 210-280°C.

[0032] The oxidation treatment time is preferably 5 to 100 minutes, for example 70 minutes.

[0033] The precursor is preferably any one of polyacrylonitrile-based carbon fiber precursor, asphalt-based carbon fiber precursor and viscose-based carbon fiber precursor, for example, polyacrylonitrile-based carbon fiber precursor.

[0034] In the present invention, the carbonization reaction may further include the steps of surface treatment, sizing treatment and drying treatment.

[0035] The present invention also provides a carbon fiber prepared by the carbonization method of the above carbon fiber.

[0036] The tensile strength of the carbon fiber can reach more than 4GPa. The bulk density of the carbon fiber can reach 1.72g / cm 3 The elongation at break of the carbon fiber can reach 1.50% or more. The carbon content of the carbon fiber can reach 91% or more.

[0037] The present invention provides a method for graphitizing carbon fiber, which comprises the following steps:

[0038] A microwave plasma torch device is used as a graphitization device, an inert gas is used as a plasma gas, and a pre-oxidized wire is passed through a plasma torch of the microwave plasma torch to perform a graphitization reaction on the pre-oxidized wire;

[0039] The number of the microwave plasma torches is at least 3, each of the microwave plasma torches corresponds to a temperature zone for graphitization reaction, and the at least 3 microwave plasma torches sequentially form a low-temperature carbonization zone, a high-temperature carbonization zone and a graphitization zone with gradually increasing temperatures along the moving direction of the pre-oxidized wire;

[0040] The low-temperature carbonization zone is the aforementioned low-temperature carbonization zone; the high-temperature carbonization zone is the aforementioned high-temperature carbonization zone;

[0041] The graphitization zone includes at least one temperature zone, the temperature of the graphitization zone is 1600-2500°C, and includes a temperature zone with a temperature of ≥1700°C.

[0042] In the present invention, carbon fiber begins to graphitize in an inert atmosphere at a temperature above 1700° C., and the higher the temperature, the faster the graphitization speed.

[0043] In the present invention, the temperature difference between adjacent temperature zones is preferably 50-500°C, more preferably 50-250°C.

[0044] In the present invention, the number of the microwave plasma torches is preferably 6 to 12, more preferably 10.

[0045] In the present invention, the graphitization zone preferably includes 2 to 3 temperature zones with gradually increasing temperature along the moving direction of the pre-oxidized wire; when the number of the temperature zones is 2, the temperatures of the two temperature zones are preferably 1850°C and 2050°C respectively; when the number of the temperature zones is 3, the temperatures of the three temperature zones are preferably 1750-1850°C, 1900-2150°C, 2200-2450°C, for example, 1760°C, 1980°C, 2250°C.

[0046] In the present invention, the reaction time of each temperature zone is 3 to 20 seconds, for example, 4 seconds, 5 seconds, 7 seconds, 10 seconds or 20 seconds.

[0047] In the present invention, the number of the microwave plasma torches may be 10, and the temperatures of the 10 temperature zones are preferably 350-400° C., 550-650° C., 700-800° C., 850-950° C., 1000-1100° C., 1150-1250° C., 1300-1400° C., 1450-1550° C., 1600-1800° C. and 1850-2000° C., for example, 350° C., 600° C., 800° C., 920, 1030° C., 1160° C., 1350, 1500° C., 1700° C., 1900° C. The reaction time of the 10 temperature zones is preferably 3-8 seconds, for example, 5 seconds.

[0048] In the present invention, the number of the microwave plasma torches is 12, and the temperatures of the 12 temperature zones are preferably 350-400° C., 550-650° C., 700-800° C., 850-950° C., 1000-1100° C., 1150-1200° C., 1230-1300° C., 1320-1400° C., 1420-1500° C., 1550-1650° C., 1680-1800° C., and 1850-2000° C., such as 350° C., 600° C., 800° C., 920, 1030° C., 1160° C., 1280, 1350° C., 1460° C., 1600° C., 1700° C., and 1900° C. The reaction time of the 12 temperature zones is preferably 3-6 seconds, such as 4 seconds.

[0049] In the present invention, the type of the inert gas and the flow rate of the inert gas are preferably the inert gas and flow rate described in the aforementioned carbonization method of carbon fibers.

[0050] In the present invention, the power of the microwave plasma torch is the power described in the carbonization method of the above-mentioned carbon fiber.

[0051] In the present invention, the carbon fiber graphitization method preferably further comprises drawing and conveying the carbon fiber.

[0052] The draft ratios of the low temperature carbonization zone and the high temperature carbonization zone are preferably consistent with those described in the carbonization method of the carbon fiber. The draft ratio of the graphitization zone is preferably -5% to 1%, more preferably -4.5% to -0.05%.

[0053] In the present invention, the method for preparing the pre-oxidized fiber is preferably the same as the method described in the carbonization method of the aforementioned carbon fiber.

[0054] The present invention also provides graphite fibers prepared by the above-mentioned carbon fiber graphitization method.

[0055] The tensile strength of the graphite fiber can reach more than 5Gpa. The bulk density of the graphite fiber can reach 1.9g / cm 3 The breaking elongation of the graphite fiber can reach more than 1.29%. The carbon content of the graphite fiber can reach more than 99%.

[0056] The positive and progressive effects of the present invention are:

[0057] (1) The microwave plasma torch used in the method of the present invention is low in price and maintenance cost. The electric energy consumed is mainly used to generate the inert gas plasma flame, and no energy is wasted on heating the furnace. The required inert gas flow is only used to maintain the plasma flame, and the demand is less than one-tenth of the traditional carbonization furnace. The energy consumption is greatly reduced while the amount of gas and cooling water is greatly reduced. The low equipment cost and operation cost also allow the carbonization process to gain a broader development space.

[0058] (2) The microwave plasma torch used in the method of the present invention as the carbonization equipment and graphitization equipment can flexibly increase or decrease the carbonization temperature zone, thereby improving the performance of the carbon fiber without increasing the equipment cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] Figure 1 Schematic diagram of the structure of carbonized fiber using microwave plasma torch equipment.

[0060] Description of the reference numerals in the accompanying drawings:

[0061] Fiber 1

[0062] Plasma Torch 2

[0063] Microwave plasma torch equipment3. DETAILED DESCRIPTION

[0064] The present invention is further described below by way of examples, but the present invention is not limited to the scope of the examples. The experimental methods in the following examples without specifying specific conditions are carried out according to conventional methods and conditions, or selected according to the product specifications.

[0065] Example 1

[0066] The specific steps of the carbon fiber preparation method of this embodiment are as follows:

[0067] (1) The polyacrylonitrile-based carbon fiber precursor was pre-oxidized in an oxidation furnace to obtain 5 bundles of pre-oxidized fibers, with a pre-oxidation temperature of 200-270°C and a pre-oxidation time of 70 min, and each bundle had 3000 fibers;

[0068] (2) Four 3kw microwave plasma torch devices were used, with argon as the plasma gas. The four microwave plasma torch devices were set in sequence, and the flame temperature and size of the microwave plasma torch devices were set by adjusting the power and argon flow rate. The argon flow rate was 10L / min. The four devices formed a low-temperature carbonization zone and a high-temperature carbonization zone with gradually increasing temperatures in sequence along the moving direction of the pre-oxidation wire. The low-temperature carbonization zone included two temperature zones, and the high-temperature carbonization zone included two temperature zones. The temperatures of the four temperature zones were 350°C, 600°C, 1150°C and 1500°C, respectively. The temperature measurement point was the position of the plasma flame through which the pre-oxidation wire was transmitted. The schematic diagram of the positional relationship between the microwave plasma torch device and the fiber is shown in Figure 1 shown.

[0069] (3) The carbon fiber is stretched and conveyed by the stretching roller, and 5 bundles of pre-oxidized fibers are simultaneously conveyed through four temperature zones of four microwave plasma torch devices for carbonization reaction. The running speed of the pre-oxidized fibers is controlled to be 5 m / min, and the reaction time in the four microwave plasma torch devices is 20 s. The roller speed accuracy of the stretching roller is controlled to be 0.0001 m / min, the stretching rate in the low-temperature carbonization zone is -1.0% to 5%, and the stretching rate in the high-temperature carbonization zone is -4.5% to 0.5%.

[0070] The carbon fiber is obtained by reaction, and then surface treatment, sizing, drying and winding are performed to obtain the carbon fiber.

[0071] Example 2

[0072] This embodiment is basically the same as Embodiment 1, except that: this embodiment uses 6 microwave plasma torch devices, the low-temperature carbonization zone includes 3 temperature zones, the high-temperature carbonization zone includes 3 temperature zones, and the temperatures of the 6 temperature zones are 350°C, 600°C, 800°C, 1050°C, 1300°C, and 1450°C, respectively; the running speed of the pre-oxidized wire is controlled to be 10m / min, and the reaction time in each temperature zone is 10s.

[0073] Example 3

[0074] This embodiment is basically the same as Embodiment 1, with the only difference being that: this embodiment uses 8 microwave plasma torch devices, the low-temperature carbonization zone includes 3 temperature zones, the high-temperature carbonization zone includes 4 temperature zones, and the temperatures of the 8 temperature zones are 350°C, 600°C, 800°C, 920, 1030°C, 1160°C, 1350, and 1500°C, respectively; the running speed of the pre-oxidized fiber is controlled to be 15m / min, and the reaction time in each temperature zone is 7s.

[0075] Example 4

[0076] This embodiment is basically the same as Embodiment 2, except that this embodiment uses nitrogen as the plasma gas.

[0077] Example 5

[0078] This embodiment is basically the same as Embodiment 2, except that: in this embodiment, the running speed of the pre-oxidized fiber is controlled to be 20 m / min, and the reaction time in each temperature zone is 5 s.

[0079] Example 6

[0080] The specific steps of the graphitized fiber preparation method of this embodiment are as follows:

[0081] (1) The polyacrylonitrile-based carbon fiber precursor was pre-oxidized in an oxidation furnace to obtain 5 bundles of pre-oxidized fibers, with a pre-oxidation temperature of 200-270°C and a pre-oxidation time of 70 min, and each bundle had 3000 fibers;

[0082] (2) Ten 3 kW microwave plasma torch devices were used, with argon as the plasma gas. The ten microwave plasma torch devices were set up in sequence, and the flame temperature and size of the microwave plasma torch devices were set by adjusting the power and argon flow rate. The argon flow rate was 10 L / min. The ten devices formed a low-temperature carbonization zone, a high-temperature carbonization zone and a graphitization zone with gradually increasing temperatures along the moving direction of the pre-oxidation wire. The low-temperature carbonization zone included three temperature zones, the high-temperature carbonization zone included five temperature zones, and the graphitization zone included two temperature zones. The temperatures of the ten temperature zones were 350°C, 600°C, 800°C, 920°C, 1030°C, 1160°C, 1350°C, 1500°C, 1850°C and 2050°C, respectively. The temperature measurement point was the position of the plasma flame through which the pre-oxidation wire was transmitted. The schematic diagram of the positional relationship between the microwave plasma torch device and the fiber is shown in the figure. Figure 1 shown.

[0083] (3) The carbon fiber is stretched and conveyed by a stretching roller, and 5 bundles of pre-oxidized fibers are simultaneously conveyed through four temperature zones of 10 microwave plasma torch devices for carbonization reaction. The running speed of the pre-oxidized fibers is controlled to be 15 m / min, and the reaction time in the four microwave plasma torch devices is 5 s. The roller speed accuracy of the stretching roller is controlled to be 0.0001 m / min, the stretching rate in the low-temperature carbonization zone is -1.0% to 5%, the stretching rate in the high-temperature carbonization zone is -4.5% to 0.5%, and the stretching rate in the graphitization zone is -4.5% to -0.05%.

[0084] The graphitized fiber is obtained by the reaction, and then the graphitized fiber is obtained through surface treatment, sizing, drying and winding.

[0085] Example 7

[0086] This embodiment is basically the same as Embodiment 6, except that: this embodiment uses 12 microwave plasma torch devices, the low-temperature carbonization zone includes 3 temperature zones, the high-temperature carbonization zone includes 7 temperature zones, the graphitization zone includes 2 temperature zones, the temperatures of the 10 temperature zones are 350°C, 600°C, 800°C, 920°C, 1030°C, 1160°C, 1280°C, 1350°C, 1460°C, 1600°C, 1850°C and 2050°C, respectively, the running speed of the pre-oxidized fiber is controlled to be 15m / min, and the reaction time in each temperature zone is 4s.

[0087] Comparative Example 1

[0088] This comparative example uses a traditional carbonization furnace as the carbonization equipment. The low-temperature furnace is a stainless steel furnace with two temperature zones, 350°C and 600°C respectively. The high-carbon furnace is a graphite furnace with two temperature zones, 1150°C and 1500°C respectively, to carbonize the pre-oxidized fibers. The running speed of the pre-oxidized fibers in the carbonization furnace is controlled to be 5m / min, the reaction time in the high-temperature carbonization furnace is 40s, and the flow rate of nitrogen is 190m / min. 3 / h; and the carbon fiber is stretched by a stretching roller, and the roller speed accuracy of the stretching roller is controlled to be 0.01m / min; the stretching rate in the low temperature carbonization zone is -1.0% to 5%, and the stretching rate in the high temperature carbonization zone is -4.5% to 0.5%. Carbon fiber is obtained.

[0089] Comparative Example 2

[0090] This comparative example uses a conventional carbonization furnace as the carbonization equipment to carbonize the preoxidized fiber. The low-temperature furnace is a stainless steel furnace with two temperature zones, 350°C and 600°C respectively. The high-carbon furnace is a graphite furnace with six temperature zones, 800°C, 1050°C, 1300°C, and 1450°C respectively. The speed of the preoxidized fiber in the carbonization furnace is controlled to be 10m / min, the reaction time in the high-temperature carbonization furnace is 40s, and the flow rate of nitrogen is 190m / min. 3 / h; and the carbon fiber is stretched by a stretching roller, and the roller speed accuracy of the stretching roller is controlled to be 0.01m / min; the stretching rate in the low temperature carbonization zone is -1.0% to 5%, and the stretching rate in the high temperature carbonization zone is -4.5% to 0.5%. Carbon fiber is obtained.

[0091] Comparative Example 3

[0092] This comparative example is basically the same as Example 3, except that this comparative example uses air as the plasma gas.

[0093] Comparative Example 4

[0094] This comparative example is basically the same as Example 3, except that this comparative example uses a 3kw capacitively coupled high-frequency plasma torch device.

[0095] Effect Example

[0096] The fibers obtained in the examples and comparative examples were tested for bulk density, tensile strength, elongation at break and carbon content. The test methods for tensile strength and elongation at break refer to the national standard: GB / T3362-2017 Test method for tensile properties of carbon fiber multifilaments; the test method for carbon content refers to the national standard GB / T 31292-2014 "Determination of carbon fiber carbon content combustion absorption method"; the test range of bulk density is obtained through multiple sampling tests of carbon fiber; the test method of bulk density refers to the national standard GB / T30019-2013 Determination of carbon fiber density.

[0097] The test results are shown in Table 1.

[0098] Table 1

[0099]

[0100]

[0101] It can be seen from the data of the embodiments and comparative examples that high-performance carbon fibers or graphitized fibers can be prepared by carbonizing or graphitizing preoxidized fibers using the method of the present invention, and the performance of the carbon fibers is similar to that of carbon fibers prepared by traditional processes.

[0102] It can be seen from the data of Examples 1-2 and Comparative Examples 1-2 that increasing the number of carbonization temperature zones can improve the performance of carbon fibers. However, in the traditional process, the carbonization furnace has a fixed structure, is expensive, has high operating costs, and it is very costly to increase the temperature zones. The inert gas plasma equipment used in the present invention has low cost and operating costs, and provides a practical solution for optimizing the carbonization process of carbon fibers and adding multiple carbonization temperature zones.

[0103] It can be seen from Examples 6 and 7 that when the number of microwave plasma torch devices is increased to more than 8, the effect of carbonizing the fibers is not significantly improved.

Claims

1. A method for carbonizing carbon fiber, characterized in that: It includes the following steps: A microwave plasma torch device is used as a carbonization device and an inert gas is used as a plasma gas, and a pre-oxidized wire is passed through a plasma torch of the microwave plasma torch to perform a carbonization reaction on the pre-oxidized wire; The number of the microwave plasma torches is at least 2, each of the microwave plasma torches corresponds to a temperature zone for carbonization reaction, and at least 2 of the microwave plasma torches sequentially form a low-temperature carbonization zone and a high-temperature carbonization zone with gradually increasing temperature along the moving direction of the pre-oxidized wire; The low temperature carbonization zone includes at least one temperature zone, and the temperature of the low temperature carbonization zone is 350-800°C; The high temperature carbonization zone includes at least one temperature zone, and the temperature of the high temperature carbonization zone is 800-1600°C.

2. The carbonization method of carbon fiber according to claim 1, characterized in that: The temperature difference between adjacent temperature zones is 50-500°C, preferably 50-250°C; And / or, the number of the microwave plasma torches is 6 to 10, preferably 8; And / or, the reaction time of each temperature zone is 3 to 20 seconds, such as 4 seconds, 5 seconds, 7 seconds, 10 seconds or 20 seconds; and / or, the running speed of the pre-oxidized wire in the microwave plasma torch is 3 to 20 m / min, for example, 5 m / min, 10 m / min or 20 m / min; And / or, the inert gas is one or more of argon, nitrogen, helium and neon, preferably argon.

3. The carbonization method of carbon fiber according to claim 1, characterized in that: The low-temperature carbonization zone includes 2 to 3 temperature zones with gradually increasing temperatures along the moving direction of the preoxidized wire. When there are 3 temperature zones, the temperatures of the 3 temperature zones are 350 to 400° C., 550 to 650° C., and 700 to 800° C., for example, 350° C., 600° C., and 800° C.; And / or, the high temperature carbonization zone includes 5 to 7 temperature zones with gradually increasing temperatures along the moving direction of the pre-oxidized wire; When there are five temperature zones, the temperatures of the five temperature zones are 850-950° C., 1000-1100° C., 1150-1250° C., 1300-1400° C. and 1450-1550° C., for example, 920° C., 1030° C., 1160° C., 1350° C. and 1500° C.; When there are 7 temperature zones, the temperatures of the 7 temperature zones are 850-950°C, 1000-1100°C, 1150-1200°C, 1230-1300°C, 1320-1400°C, 1420-1500°C and 1550-1650°C, for example, 920°C, 1030°C, 1160°C, 1280°C, 1350°C, 1460°C and 1600°C.

4. The carbonization method of carbon fiber according to claim 1, characterized in that: The method for preparing the pre-oxidized yarn comprises: subjecting the raw yarn to oxidation treatment in an oxidation furnace to obtain the pre-oxidized yarn; The temperature of the oxidation treatment is preferably 210-280° C., the time of the oxidation treatment is preferably 5-100 min, for example 70 min, and the precursor is preferably any one of polyacrylonitrile-based carbon fiber precursor, asphalt-based carbon fiber precursor and viscose-based carbon fiber precursor, for example, polyacrylonitrile-based carbon fiber precursor.

5. The carbonization method of carbon fiber according to claim 1, characterized in that: The carbonization method of the carbon fiber also includes stretching and conveying the carbon fiber, wherein the stretching rate of the low-temperature carbonization zone is -8% to 8%, preferably -1.0% to 4.0%; the stretching rate of the high-temperature carbonization zone is -6% to 3%, preferably -4.0% to 0.5%; And / or, the carbonization reaction further includes the steps of surface treatment, sizing treatment and drying treatment.

6. A method for graphitizing carbon fiber, characterized in that: It includes the following steps: A microwave plasma torch device is used as a graphitization device, an inert gas is used as a plasma gas, and a pre-oxidized wire is passed through a plasma torch of the microwave plasma torch to perform a graphitization reaction on the pre-oxidized wire; The number of the microwave plasma torches is at least 3, each of the microwave plasma torches corresponds to a temperature zone for graphitization reaction, and the at least 3 microwave plasma torches sequentially form a low-temperature carbonization zone, a high-temperature carbonization zone and a graphitization zone with gradually increasing temperatures along the moving direction of the pre-oxidized wire; The low-temperature carbonization zone and the high-temperature carbonization zone are the low-temperature carbonization zone and the high-temperature carbonization zone described in the carbonization method of carbon fiber according to any one of claims 1 to 5; The graphitization zone includes at least one temperature zone, the temperature of the graphitization zone is 1600-2500°C, and includes a temperature zone with a temperature of ≥1700°C.

7. The method for graphitizing carbon fiber according to claim 6, characterized in that: The temperature difference between adjacent temperature zones is 50-500°C, preferably 50-250°C; And / or, the number of the microwave plasma torches is 6 to 12, preferably 10; And / or, the reaction time of each temperature zone is 3 to 20 seconds, such as 4 seconds, 5 seconds, 7 seconds, 10 seconds or 20 seconds; and / or, the running speed of the pre-oxidized wire in the microwave plasma torch is 3 to 20 m / min, for example, 5 m / min, 10 m / min or 20 m / min; And / or, the inert gas is one or more of argon, nitrogen, helium and neon, preferably argon.

8. The method for graphitizing carbon fiber according to claim 7, characterized in that: The graphitization zone includes 2 to 3 temperature zones with gradually increasing temperature along the moving direction of the pre-oxidized wire. When there are 2 temperature zones, the temperatures of the 2 temperature zones are 1850°C and 2050°C respectively; when there are 3 temperature zones, the temperatures of the 3 temperature zones are 1750-1850°C, 1900-2150°C and 2200-2450°C respectively, for example, 1760°C, 1980°C and 2250°C.

9. The method for graphitizing carbon fiber according to claim 7, characterized in that: The method for preparing the pre-oxidized yarn comprises: subjecting the raw yarn to oxidation treatment in an oxidation furnace to obtain the pre-oxidized yarn; The temperature of the oxidation treatment is preferably 210-280° C., the time of the oxidation treatment is preferably 5-100 min, for example 70 min, and the precursor is preferably any one of polyacrylonitrile-based carbon fiber precursor, asphalt-based carbon fiber precursor and viscose-based carbon fiber precursor, for example, polyacrylonitrile-based carbon fiber precursor.

10. The method for graphitizing carbon fiber according to claim 7, characterized in that: The carbon fiber graphitization method also includes stretching and conveying the carbon fiber, wherein the stretching rate of the low-temperature carbonization zone is -8% to 8%, preferably -1.0% to 5.0%; the stretching rate of the high-temperature carbonization zone is -6% to 3%, preferably -4.5% to 0.5%; and the stretching rate of the graphitization zone is -5% to 1%, preferably -4.5% to -0.05%.

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